1 . Field of the Invention
This invention generally relates to cooling systems for electronic circuitry and, in particular, to cooling systems for electronic circuit board modules, especially those used in aerospace applications.
2. Description of the Related Art
When designing electrical equipment for use in aerospace applications, designers have often been forced to trade the desirable characteristics of low weight and compact size for larger and heavier configurations to achieve sufficient cooling of the circuitry to insure reliability and extended service life. In today's complex high speed electronic instruments, the heat produced is substantial and various techniques have been proposed for cooling the electronic modules. Many of the proposed techniques involve use of cold plates in physical contact with the electronic circuit boards, or elaborate forced air or fluid cooling designs to transfer heat away from the electronic circuits. Each of these arrangements adds undesirable weight and complexity to the instrument.
In the typical aerospace application, the electronic modules must also be easily accessible for replacement, testing, and repair. In many applications, ease of service of the componentry is so critical as to preclude the use of systems using elaborate cooling methods.
Electronic components are typically arranged on circuit boards that are arranged to form an electronic module. The individual circuit boards are clamped to guide rails in the module housing, and the guide rails may be designed to conduct heat away from the circuit board to a mounting plate. Forced air or circulating fluid is then used to cool the plate. An example of such an arrangement is found in U.S. Pat. No. 5,057,968 issued to Morrison. This method is sometimes inadequate, especially where many circuit boards are mounted within an instrument, because the surface area of the mounting plate may be insufficient to ensure adequate heat transfer from the guide rails.
Until recently, the guide rails and module housing needed to be formed of heat conducting metals, such as aluminum, aluminum/beryllium alloy, (for example "ALBEMET" available from Brushwellman, Cleveland, Ohio) or other suitable materials. The disadvantage of these materials is that while they have high coefficients of thermal-conductivity, they add substantial weight to the module and thus the overall system.
From the above, it can be seen that a need exists for a low weight, highly thermally-conductive circuit board guide rail system that can securely hold an electronic circuit board and still conduct enough heat away from the board to prevent thermal damage. The present invention fulfills this need.